Advanced Issues in
Humidification
Presented by:
Ruben Restrepo MD, RRT, FAARC
Professor , Department of Respiratory Care
The University of Texas
Health Science Center, San Antonio
Disclosures
TELEFLEX MEDICAL
Medical Advisory Board
Speaker
COVIDIEN
Speaker, Consultant, and Investigator
SALTER LABS
Speaker and Consultant
FISHE & PAYKEL
Investigator
1. Discuss the impact of high and low ambient
temperatures on heated humidification
2. Describe the role of inlet chamber gas temperatures on
overall delivery of humidity
3. Discuss ventilator settings associated with significant
changes in humidification
4. Discuss the relationship between aerosol therapy and
heated humidification
Isothermic Saturation Boundary
Why Humidity Deficit?
• Effect of intubation
• Inspired gas AH is < BTPS
• ISB is shifted down the
respiratory tract
• Humidity comes from the
lower respiratory tract
• Increased heat and
moisture loss from the
airways
Teleflex Advances in Respiratory Therapy. Humidification Basics: Module 1 2010-0032
Typical Humidity Values
Medical Gases
Room Air
Alveoli
15ºC
20ºC
37ºC
RH
0-2%
50-60%
100%
AH
0-0.5 mg/L
8.7-10.4 mg/L
44 mg/L
Temperature
RH 50% = not exactly 22 mg/L
Supplemental
heat and humidity
Teleflex Advances in Respiratory Therapy. Humidification Basics: Module 1 2010-0032
Adequate Humidification
• Heated humidification devices should at least mimic the
physiologic conditions
Temperature
>340C
Adequate
Humidification
Relative
Humidity
100%
Teleflex Advances in Respiratory Therapy. Humidification Basics: Module 1 2010-0032
Absolute
Humidity
33.8-37.6
Mg H2O/L
• Humidification of inspired
gases is standard of care
for patients receiving
mechanical ventilation
(MV).1
• Inadequate humidification → deleterious effects
on airway mucosa.2
• Challenges:
• Type of humidification device used
• Issues external to humidifier’s function
1. AARC CPG. Respir Care 2012;12(57)5:782-788
2. Williams R, et al. Crit Care Med. 1996;24:1920-1929.
•Recommended min water content (AH)
≥ 33 mg H2O/L of air (AH) = 75% RH
•Optimal AH
44 mg H2O/L at body Tº (37ºC) = 100% RH
37ºC for outlet
chamber
•Heating unit should self-terminate at
Tº < 43ºC1 (tracheal thermal injury)
•Most HHs meet recommended Tº settings at
normal conditions2,3
43ºC at the Y piece
1. ISO 8185:2007 (3rd Ed)
2. Williams RB. Respir Care Clin N Am. 1998;4(2):215-28.
3. AARC Clinical Practice Guideline. Respir Care. 2012:12(57)5:782-788
AARC Clinical Practice Guideline
Humidification During Invasive and Noninvasive
Mechanical Ventilation: 2012
Ruben D Restrepo MD RRT FAARC and Brian K Walsh RRT-NPS FAARC
9
We searched the MEDLINE, CINAHL, and Cochrane Library databases for articles published
between January 1990 and December 2011. The update of this clinical practice guideline is based
on 184 clinical trials and systematic reviews, and 10 articles investigating humidification during
invasive and noninvasive mechanical ventilation. The following recommendations are made following the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) scoring
system: 1. Humidification is recommended on every patient receiving invasive mechanical ventilation. 2. Active humidification is suggested for noninvasive mechanical ventilation, as it may improve
adherence and comfort. 3. When providing active humidification to patients who are invasively
ventilated, it is suggested that the device provide a humidity level between 33 mg H2O/L and
44 mg H2O/L and gas temperature between 34°C and 41°C at the circuit Y-piece, with a relative
humidity of 100%. 4. When providing passive humidification
to patients
undergoing
invasive
AARC Clinical Practice
Guideline.
Respir Care.
2012:12(57)5:782-788
mechanical ventilation, it is suggested that the HME provide a minimum of 30 mg H2O/L. 5. Passive
humidification is not recommended for noninvasive mechanical ventilation. 6. When providing
KEY POINTS
Although modern active humidifiers can deliver gas at 41ºC at
the Y-piece, a maximum delivered gas temperature of 37ºC
and 100% RH (44 mg H2O/L) at the circuit Y-piece is
recommended.
Insufficient heat and humidification can occur with HHs.
Complications can occur when temperature selection is preset
and nonadjustable, rather than based on clinical assessment.
NIV. Select gas temperatures during NIV based on patient
comfort/tolerance/adherence and underlying pulmonary
condition.
Change circuits as needed due to lack of functionality or when
visibly soiled, unless otherwise specified by the manufacturer.
AARC Clinical Practice Guideline. Respir Care. 2012:12(57)5:782-788
10
AARC Clinical Practice Guideline. Respir Care. 2012:12(57)5:782-788
1
2
3
4
5
6
7
Every patient receiving invasive mechanical ventilation should get humidification.
(1A)
Active humidification is suggested for NIV, as it may improve adherence and
comfort. (2B)
When providing active humidification to patients who are invasively ventilated,
the device should provide a humidity level between 33 mg H2O/L and 44 mg
H2O/L, and a gas temperature between 34ºC and 41ºC at the circuit Y-piece, with
an RH of 100%. (2B)
When providing passive humidification to patients undergoing invasive
mechanical ventilation, the HME should provide a minimum of 30 mg H2O/L. (2B)
Passive humidification is not recommended for NIV. (2C)
When providing humidification to patients with low tidal volumes, such as when
lung-protective ventilation strategies are used, HMEs are not recommended
because they contribute additional dead space, which can increase the ventilation
requirement and PaCO2. (2B)
HMEs should not be used as a prevention strategy for ventilator-associated
pneumonia.(2B)
• Factors that affect active humidification
•
•
•
•
•
Ambient temperature
Type of heater humidifier
Ventilator type and ventilator settings
Placement and removal of SVNs during MV
Humidification and heat effects on aerosol delivery
• Factors that affect passive
humidification
• Accumulation of condensate
• Routine aerosol administered without
bypassing the HME
• Increase airway resistance
NIV reduces rate of intubations and adverse
effects associated with invasive MV and
bypassing the airway.1,2
Humidification delivery for these
patients is still not considered standard
of care in all clinical settings.
1. Ambrosino, N Int J Chron Obstruct Pulmon Dis. 2007 December; 2(4): 471–476.
2. James CS, et al. Intensive Care Med 2011;37(12):1994-2001
 HHs are considered the most efficient
method of optimizing gas for patients with an
artificial airway.1,2
 HHs have been associated with higher
rates of obstruction of artificial airway than
HMEs.3
1. Ricard JD, et al. Chest. 1999;115:1646-1652.
2. Diehl JL, et al. Am J Respir Crit Care Med. 1999;159:383–388.
3. Lacherade J-C, et al. Am J Respir Crit Care Med. 2005;172:1276-1282. .
• Good understanding of HH function and how
different clinical conditions is critical.
• HHs control Tº, not humidity levels.
• Gas Tº at the HH inlet can be as high as 40ºC
(dry part of circuit).


Lellouche F, et al. Am J Respir Crit Care Med. 2004;170:1073-1079.
Heated Humidifier
• Gas passes over heated water
 Humidity of gas ↑ as Tº of gas ↑
 Humidity is controlled by manipulating
water temperature in the reservoir
• Modified passover design
 Paper wick increases surface area
Ventilator
°
Example:
Chamber T = 37°
Humidifier
Chamber
Routine check of the HH and breathing circuit:
• Small amount of condensate or “rainout” = visible sign of
humidity production
• Amount of condensate ≈ rate of water loss from the chamber
• May indicate suboptimal Tº setting in the HH
• Possible adjustments:
 Lowering humidifier T°
 Heated-wires can control Tº drop between the HH and
the patient → reduce condensate
• Ambient air temperatures
• Humidifier inlet gas temperature (ventilator
outlet gas temperature)
• Ventilator settings (including flows and minute
volumes)
• Concomitant use of aerosol therapy while
administering active humidification
• Ambient air temperatures (high vs. low)
• Humidifier inlet gas temperature (Ventilator
outlet gas temperature)
• Ventilator settings (including flows and minute
volumes)
• Concomitant use of aerosol therapy while
administering active humidification
• High ambient Tº = greatest influence on HH
performance.1
• Ambient Tº in ICUs 22.0ºC‒30.0ºC.
• Factors associated with increased ambient air
Tº:




Inadequate air conditioning
Burn units
Neonatal units2
Warm conditions proximal to the humidifier
1. Lellouche L, et al. Am J Respir Crit Care Med. 2004;1073-1079.
2. Todd DA, et al. J Paediatr Child Health. 2001;37(5):489-94.
▼ Humidity Level
Dry Hot Air
Ambient air Tº > 28-30ºC
▼
Reduction in humidity levels
Increased inlet Tº prevents heater plate
warming water inside the chamber
Lower Heater Plate Tº
1. Lellouche L, et al. Am J Respir Crit Care Med. 2004;1073-1079.
Large drops in ambient Tº
▼
Cooling of gas travels through the humidifier and circuit
▼
excess condensate
(avoid “lavaging” patient’s airway)
• Ambient air temperatures
• Humidifier inlet gas temperature (ventilator
outlet gas temperature)
• Ventilator settings (including flows and minute
volumes)
• Concomitant use of aerosol therapy while
administering active humidification
• High inlet gas Tº = lower humidity production:1
 From ≈ 36 mg H2O/L at chamber temp 18ºC
Dry Hot Air
(82% relative humidity at 37ºC)
 To 26 mg H2O/L at 32ºC
(59% relative humidity at 37ºC)
▼ Humidity Level
Lower Heater Plate Tº
• Critical impact on the amount of condensate in
Carter BG, J Aerosol Med. 2002;15:7-13.
the breathing circuit
International Organization for Standardization. ISO 8185:2007
• Most commonly used MVs in ICUs warm oxygen
and air.
• Warming effect of different ventilators shown in
several studies evaluating ventilator outlet gas
Tº.1,2
• High speeds of turbine-powered vs. gas-powered
ventilators generate the highest outlet Tº.2
 LTV-1000
 Vela
1. Carter BG, J Aerosol Med. 2002;15:7-13.
2. Lellouche L, et al. Am J Respir Crit Care Med. 2004;1073-1079.
Ventilator
Ventilator Outlet Gas Tº
Min–Max T (ºC)
VIP
29.6 - 33.2
T Bird
36.0 – 45.1
Infant Star
27.9 - 30.0
EVITA 2
27.9 - 29.6
EVITA 4
30.2 – 35.8
3100A
24.4 - 27.3
USE THIS SLIDE OR
FOLLOWING
1. Carter BG,SLIDE
J Aerosol Med. 2002;15:7-13.
Lellouche L, et al. Am J Respir Crit Care Med. 2004;1073-1079.
• Extending length of inspiratory tubing prior to
the heating chamber (“drop line”) may offset
high Tº at the gas outlet.
 Drop line allows humidifier inlet Tº to decrease.
• Ambient air temperatures
• Humidifier inlet gas temperature (Ventilator
outlet gas temperature)
• Ventilator settings (pressure, flow and VE)
• Concomitant use of aerosol therapy while
administering active humidification
• Increases in Paw, VE, and flow increase ventilator load =
increased operating Tº of most ventilator driving systems.
• High VE reduces the time
gas stays in the water
reservoir, significantly
decreasing HH
performance.
• Changes in I:E ratio and
inspiratory flow do not
affect Tº or humidity.
Nishida T, et al. J Aerosol Med. 2001;14(1):43-51.
• Ambient air temperatures
• Humidifier inlet gas temperature (Ventilator
outlet gas temperature)
• Ventilator settings (including flows and minute
volumes)
• Concomitant use of aerosol therapy while
administering active humidification
• Humidification is essential for patients on MV
receiving aerosolized medications.
• Effects of humidification on aerosol delivery and
lung deposition may differ according to the type
of system used.
• Ventilator
• Circuit
• Type of circuit
• Inhaled gas humidity
• Inhaled gas density
•
•
•
•
Type of Interface
Device nebulizer / pMDI
Drug
Patient
Dhand R. J Aerosol Med Pulm Drug Deliv. 2012;25(2):63-78.
• Aerosol delivery is proportional to gas Tº change in
the ventilator circuit.
• 25ºC to 37ºC = increase inhaled drug mass up to 25%.
(faster evaporation = accelerates delivery rate of small
particles).1
• Positive effect of higher gas Tº on aerosol efficiency is
negated by drastic effects of increased water vapor in the
delivered gas.2,3
• Aerosol delivery is INVERSELY proportional to water
vapor content in the ventilator circuit.
1. Lange Am J Respir Crit Care Med Vol 161. pp 1614–1618, 2000
2.. Garner SS Pharmacotherapy. 1994;14:210-214.
3. Dhand R, et al. Eur Respir J. 1996; 9(3):585-595.
SVN
•High RH and Tº in circuit = large reductions of lung dose.
pMDI
No significant differences on mass median aerodynamic
diameter (MMAD) with dry vs. high RH.1
•Clinicians often turn off HH before administering aerosols.
 Failure to turn on after tx = inadequate humidification.
 Turning heater off prior to tx does not result in greater
aerosol drug delivery.
1. Lin HL, et al. Respir Care. 2009;54(10):1336-41.
2. Lange C, et al. Am J Respir Crit Care Med. 2000;161(5):1614-1618.
3. Zhou Y, et al. J Aerosol Med. 2005;18(5):283-293.
4. Kim CS, et al. Am Rev Respir Dis. 1985;132(1):137-142.
O’Riordan TG, et al. Am Rev Respir Dis. 1992;145:1117–1122.
Fink JB, et al. Am J respir Crit Care Med 1996;154:382-387
Fuller HD, et al. Chest 1994;105:214-218
Diot P, et al. Am J Respir Crit Care Med 1995;152:1391-1394
1. Fink, et al. Am J Respir Crit Care Med. 1996;154:382-387.
2. Ari A, et al. Respir Care. 2010;55:837-44.
Aerosol Placement and HH Function
• Placement of the aerosol generator device affects
aerosol delivery efficiency and may also affect HH.
• Heated wires prevent placement of aerosol devices
halfway between the humidifier and the Y piece.
• If a SVN is placed at the humidifier outlet chamber,
cold gas may cause humidifier overheating.
• Placement of nebulizer at the inlet of the HH chamber
will prevent overheating, as the aerosol and gas from
the ventilator are heated before exiting the humidifier,
potentially improving drug deposition.
Ari A, et al. Respir Care. 2010;55:837-44.
• The level of humidification in NIV is influenced by
several factors.
• Optimal humidification may affect dosing.
Dhand R. J Aerosol Med Pulm Drug Deliv. 2012;25(2):63-78.
Aerosol Generator Placement and HME
• Use of HMEs is a routine practice in many ICUs.
• It is common to place the aerosol generator between the
HME and the Y piece to administer aerosolized
treatments to patients receiving MV.
• Contraindication for HME use = need for aerosol therapy
• Performance of HHs can be greatly affected
by conditions external to humidifier function.
• High ambient air Tº is associated with high
inlet chamber temperatures and poor HH
performance.
• Very high ambient Tº, the Tº of the chamber water may be too
low to evaporate—causing an extremely low level of AH.
• To optimize HH performance, closely monitor
inlet chamber gas Tº.
• The presence of heated wires may help only to
maintain the set outlet chamber Tº.
• Varying Tº gradients vs. using fixed Tº gradient
(i.e., between the outlet chamber and Y piece
Tº) may improve humidification in a variety of
clinical scenarios.
• Alternatively, use compensation features
incorporated into some HHs.
Lin, H RESPIRATORY CARE • OCTOBER
Lellouche
L, et
al.10
Am J Respir Crit Care Med. 2004;1073-1079.
2009
VOL 54
NO
• There is a dramatic reduction of aerosol
delivery in humidified conditions.
• Conditions that facilitate the accumulation of
condensate on the ventilator circuit and the
spacer may adversely affect aerosol lung
delivery and clinical response.
Lin, H RESPIRATORY CARE • OCTOBER 2009 VOL 54 NO 10
• Humidification devices that control the
humidifier outlet Tº independently of
ambient air Tº, ventilator gas output, or
ventilator settings appear to be the
logical approach to optimizing humidifier
function.
Additional Information
• This webinar is archived on www.clinicalfoundations.org